Wire based temperature sensing electrode

ABSTRACT

Systems and methods are described for a wire based temperature sensing electrode for surgical procedures. A temperature sensing energy delivery device includes an elongated member having a groove formed in at least portion of the elongated member; and a first temperature sensor mechanically connected to the elongated member, the first temperature sensor including a first temperature sensor lead that is routed along the groove. The systems and methods provide advantages in that the wire based temperature sensing electrode for surgical procedures can simultaneously accommodate a temperature sensor and associated leads, exhibit sufficient strength without bulk, and be provided at lower cost.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to the field of electrodes for medicaltreatment. More particularly, the invention relates to a wire basedelectrode that is provided with a temperature sensing capability withoutnecessarily needing to use any hollow tubing to accommodate thecorresponding temperature sensor lead.

2. Discussion of the Related Art

Prior art temperature sensing electrodes, sometimes called temperaturesensing energy delivery devices, are known to those skilled in the art.For example, a conventional temperature sensing electrode is typicallyconstructed by threading a thermocouple cable through the central axisof a hollow tube and fixing the junction of the thermocouple to asharpened tip at a distal end of the hollow tube.

Referring to FIG. 1, a conventional temperature sensing electrode isshown. A stainless steel tube 100 is provided with a sharpened tip 110.The junction 120 of a thermocouple 130 is attached to the interior ofthe stainless steel tube 100 with an adhesive 140. The thermocouple 130includes a first wire 140 of a first metal material and a second wire150 of a second metal material.

A problem with this temperature sensing electrode technology has beenthat using a hollow tube to accommodate the thermocouple cable reducesthe strength of the electrode, compared to a non-temperature sensing,solid wire electrode of equal outer diameter. In the past, in order toaddress this reduction in strength, the size (i.e., inner and outerdiameter) of the hollow tubing was increased to achieve the necessarymechanical strength. However, this scaling-up approach has the twindrawbacks of creating a larger surgical instrument that is moredifficult for the surgeon to manipulate and an instrument which cuts alarger hole when inserted into tissue, thereby increasing theinvasiveness of a given surgical procedure. Therefore, what is requiredis a solution that provides a temperature sensing capability in anelectrode without increasing the bulk of the electrode.

Another problem with this temperature sensing electrode technology hasbeen that the available hollow tubing that is suitable for surgicalinsertion into tissue (i.e., tubing having suitable mechanical andcorrosion properties) is expensive. In the past, the high cost of hollowtubing based electrodes has simply been endured, thereby inhibiting thewider deployment of temperature sensing electrodes within the surgicalcommunity. Therefore, what is also required is a solution that allowsthe fabrication of a temperature sensing electrodes at lower cost,preferably a much lower cost.

Heretofore, the requirements of accommodating a temperature sensor andthe corresponding temperature sensor lead, providing sufficient strengthwithout bulk, and lower cost referred to above have not been fully metwith regard to temperature sensing electrodes. What is needed is asolution that simultaneously addresses all of these requirements.

SUMMARY OF THE INVENTION

A primary object of the invention is to provide a wire based temperaturesensing electrode. Another primary object of the invention is to providea method of using a wire based temperature sensing electrode. Anotherprimary object of the invention is to provide a method of making a wirebased temperature sensing electrode. Another primary object of theinvention is to provide a wire based temperature sensing electrode madein accordance with the method.

In accordance with these objects, there is a particular need for a wirebased temperature sensing electrode that includes a temperature sensorwhose lead is routed along a groove that is formed in the side of awire, the wire of the electrode being insertable into the tissue of apatient in need thereof. Thus, it is rendered possible to simultaneouslysatisfy the above-discussed requirements of i) accommodating atemperature sensor and the corresponding lead of the temperature sensor,ii) sufficient strength without bulk, and iii) low cost, which, in thecase of the prior art, are mutually contradicting and cannot besimultaneously satisfied.

A first aspect of the invention is implemented in an embodiment that isbased on a temperature sensing energy delivery device, comprising: anelongated member having a groove formed in at least portion thereof; anda first temperature sensor mechanically connected to said elongatedmember, said first temperature sensor including a first temperaturesensor lead that is routed along said groove.

A second aspect of the invention is implemented in an embodiment that isbased on a temperature sensing energy delivery device, comprising: anelongated member; a tube substantially coaxially connected to a distalend of said elongated member, said tube including a temperature sensorlead slot; and a first temperature sensor located within said tube, saidfirst temperature sensor having a temperature sensor lead that is routedthrough said temperature sensor lead slot.

A third aspect of the invention is implemented in an embodiment that isbased on a method of using a temperature sensing energy delivery device,comprising: providing the temperature sensing energy delivery device;inserting the temperature sensing energy delivery device into a patientin need thereof; and delivering energy to the patient through the energydelivery device.

A fourth aspect of the invention is implemented in an embodiment that isbased on a method of making a temperature sensing energy deliverydevice, comprising: mounting a distal end of an elongated member so thata portion of a length defined by said elongated member is heldsubstantially rigid; bending a proximal end of said elongated memberaway from a principle axis defined by the distal end of said elongatedmember when said elongated member is not bent; and cutting a groove withan electrostatic discharge machining wire.

These, and other, objects and aspects of the invention will be betterappreciated and understood when considered in conjunction with thefollowing description and the accompanying drawings. It should beunderstood, however, that the following description, while indicatingpreferred embodiments of the invention and numerous specific detailsthereof, is given by way of illustration and not of limitation. Manychanges and modifications may be made within the scope of the inventionwithout departing from the spirit thereof, and the invention includesall such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

A clear conception of the advantages and features constituting theinvention, and of the components and operation of model systems providedwith the invention, will become more readily apparent by referring tothe exemplary, and therefore nonlimiting, embodiments illustrated in thedrawings accompanying and forming a part of this specification, whereinlike reference characters (if they occur in more than one view)designate the same parts. It should be noted that the featuresillustrated in the drawings are not necessarily drawn to scale.

FIG. 1 illustrates a schematic view of a conventional temperaturesensing electrode, appropriately labeled "prior art."

FIGS. 2A-2B illustrate schematic views of a wire based temperaturesensing electrode, representing an embodiment of the invention.

FIG. 3 illustrates a schematic view of a wire based temperature sensingelectrode inserted into tissue, representing an embodiment of theinvention.

FIGS. 4A-4B illustrate schematic views of a wire based temperaturesensing electrode, representing an embodiment of the invention.

FIG. 5 illustrates a schematic view of a wire based temperature sensingelectrode, representing an embodiment of the invention.

FIG. 6 illustrates a schematic view of tooling for wire electrostaticdischarge machining a needle, representing an embodiment of theinvention.

FIGS. 7A-7D illustrate schematic views of a needle that has undergonewire electrostatic discharge machining, representing an embodiment ofthe invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The invention and the various features and advantageous details thereofare explained more fully with reference to the nonlimiting embodimentsthat are illustrated in the accompanying drawings and detailed in thefollowing description. Descriptions of well known components andprocessing techniques are omitted so as not to unnecessarily obscure theinvention in detail.

The context of the invention is surgical procedures with energy deliverydevices (e.g., electrodes), particularly radio frequency (RF) poweredelectrodes. The invention can also be utilized in conjunction with dataprocessing methods that transform the electrode power waveform signals(e.g., RF) that are coupled to the electrode so as to provide powercontrol, as well at to actuate additional interconnected discretehardware elements, such as, for example, auxiliary electrodes and/orfluid handling devices.

Referring to the drawings, a detailed description of preferredembodiments of the invention is provided with respect to FIGS. 2Athrough 7D. These drawings depict various aspects of an electrodestructure for accommodating at least one temperature sensor andassociated leads. The electrode structure must be capable of bothaccommodating the sensor(s) and conveying the leads to the location onthe electrode at which the temperature sensor(s) is(are) to be located.

Referring now to FIGS. 2A-2B, a nickel-titanium wire 210 includes asharp tip 220 at a distal end 230. The nickel-titanium wire 210represents a generic class of elongated members and is provided with agroove 240. A thermocouple 250 is routed through the groove 240. Thethermocouple 250 represents a generic class of temperature sensors. Thethermocouple 250 can be a copper-constantan thermocouple. Thethermocouple 250 includes a sensor lead that is routed along the groove240. The thermocouple 250 is held in place with an adhesive, such as,for example, an epoxy. The adhesive physically connects the sensor leadto the groove 240 and fills a portion of the conduit defined by thegroove 240 that is not occupied by said first temperature sensor. Thethermocouple 250 includes a sensing tip that is mechanically connectedto the groove 240 at a position that is located substantially at adistal end of the wire 210. The combined assembly can compose a surgicalinstrument for delivering energy to a life form. (It should be notedthat the surface of a tissue is represented in FIGS. 2A-2B with a wavyline for improved clarity.) Although the preferred embodiment shown inFIG. 1 includes a single thermocouple, it is within the level ofordinary skill in the art after having knowledge of the inventiondisclosed herein to add additional grooves and/or thermocouples.

It can be seen from FIGS. 2A-2B that the effect of routing thethermocouple 250 through the groove 240 is to maintain the circularouter shape of the wire 210 at its distal end. However, thecross-sectional continuity, and rotational symmetry of metal isdisrupted due to the presence of the groove 240.

When the depth of the groove is excessively low, the epoxy, and even thethermocouple wires, may protrude above the surface of the wire. On theother hand, when the depth of the groove is excessively high, themechanical integrity and/or RF performance of the wire may becompromised.

When the width of the groove is excessively low, the epoxy may not flowin the groove, and the thermocouple wires may not fit in the groove. Onthe other hand, when the width of the groove is excessively high, themechanical integrity and/or RF performance of the wire may becompromised.

The particular manufacturing process used for forming the groove 240should be inexpensive and reproducible. Conveniently, the groove 240 canbe formed using any metal cutting method. It is preferred that theprocess be electrostatic discharge machining. For the manufacturingoperation, it is moreover an advantage to employ a wire electrostaticdischarge machining method (described below in more detail).

However, the particular manufacturing process used for forming thegroove is not essential to the energy delivery device as long as itprovides the described transformation. Normally those who make or usethe invention will select the manufacturing process based upon toolingand energy requirements, the expected application requirements of thefinal product, and the demands of the overall manufacturing process.

The cutting sharp tip 220 of the electrode can be formed as a cone(coaxial or noncoaxial with the principle axis of the elongated member;and cylindrically symmetric or asymmetric). Alternatively, the cuttingsharp tip 220 of the electrode can be formed as a pyramid (e.g., a threesided pyramid, {a.k.a. a tri-bevel grind}). Conveniently, the tip 220can be formed using an metal cutting method. These tip configurationscan be provided on the distal end of the wire, or (with regard toembodiments described below) on the distal end of an attached tube, inthe embodiments where a tube is connected to the distal end of the wire.

Referring now to FIG. 3, a wire based electrode 310 is depicted in thecontext of tissue penetration during a surgical procedure. The electrode310 includes a superelastic wire 315 having a groove 320 in which ispositioned a first thermocouple 330 (tip denoted T₁). The dashed linerepresents an isotherm. The electrode 310 is at least partiallysurrounded by an layer of insulation 340. The layer of insulation canadvantageously include heat shrink tubing. A distal end of the layer ofinsulation 340 is inserted to a depth "d" beneath the surface of thetissue. The layer of insulation 340 substantially prevents heating ofthe tissue surrounding the layer of insulation 340. A secondthermocouple 350 (tip denoted T₂) is positioned between the superelasticwire 315 and the layer of insulation 340. The second thermocouple 350can be termed a safety device because it can signal an undesirableheating of tissue too near the surface. (It should be noted that thesurface of a tissue is represented in FIG. 3 with a wavy line forimproved clarity.)

FIG. 3 demonstrates substantially improved results that are unexpected.These results are represented by the dashed line that illustrates anisotherm. While not explicitly depicted in the two dimensional drawing,the isotherm is substantially cylindrically symmetric. Specifically, asubstantially constant energy delivery rate results from the use of theelectrode as θ is varied from 0 to 2π (R and r constant). Thisdemonstrates the significant unexpected advantageous result that when agroove is cut in a wire based energy delivery device, the cylindricalsymmetry of the energy field is not appreciably disrupted.

Referring now to FIGS. 4A-4B, an alternative embodiment of the inventionis shown where a tube 410 is mechanically connected to a nickel-titaniumwire 420. The tube 410 has a sharp tip 415. The tube 410 can be ahypotube. At least a portion of the tube 410 surrounds at least aportion of the wire 420. The tube 420 includes a temperature sensor leadslot 430. A thermocouple 440 is routed through the temperature sensorlead slot 430 and through at least a portion of the conduit defined bythe tube 420. The thermocouple 440 is attached to the interior of thetube 410 with an adhesive.

The temperature sensor lead slot 430 in the tube 410 is preferablyformed before the tube 410 is joined to the wire 420. Alternatively, thetemperature sensor lead slot 430 can be formed after the tube 410 isjoined to the wire 420. The temperature sensor lead slot 430 can beformed by machining, such as cutting or grinding, or by any otherforming technique that yields an orifice suitable for routing thetemperature sensor lead. (It should be noted that the surface of atissue is represented in FIGS. 4A-4B with a wavy line for improvedclarity.)

Referring now to FIG. 5, an insulating tubing 510 surrounds a wire 520and a portion of a tube 530. A first thermocouple 540 is threadedbeneath the tubing 510 and routed through a temperature sensor lead slot550 that is formed in the tube 530. A tip T₁ of the first thermocouple540 is located at a distal end 580 of the tube 530. A secondthermocouple 560 is threaded beneath the tubing 510 along at least aportion of the wire 520 and at least a portion of the tube 530. A tip ofthe second thermocouple 560 is located at a distal end 570 of the tubing510.

The temperature sensor lead slot 550 in the tube 530 can be processed byswaging or cold forging. Swaging can include squeezing one, or both, ofthe sides of the slot 550 that are parallel to a principle axis definedby the tube 530 so as to deform the side(s) to an appreciably differentshape. For example, a force can be applied to the side(s) of the leadslot from the outside of the tube. Meanwhile, the remainder of the outerdiameter of the tube can be rigidly supported. Optionally, a support pincan be inserted into the tube before the force is applied so as tobetter support the tube wall. The support pin can have one, or more,recess grooves that are opposite the direction in which the force isapplied, thereby providing clearance and room for the deformed side(s)to travel in toward the principle axis of the tube. In this way, one ormore internal ribs 590 can be formed within the tube to strengthen thetube against the weakness caused by the formation of the temperaturesensor lead slot 550. The squeezing force should be applied to arelatively small area of the tube while the strained portion of the tubehas freedom to flow without restraint.

Referring to FIG. 6, a distal end 610 of a superelastic nickel titaniumwire 620 is mounted so that a portion of a length defined by wire 620held in a substantially rigid position. A proximal end 630 of thesuperelastic nickel titanium wire 620 is deflected by a pinion 640 sothat the wire 620 is non-plastically deformed. The pinion 640 bends aproximal end of the wire 620 away from a principle axis defined by thedistal end of the wire 620. In this way, an electrostatic dischargemachining wire 650 can cut a groove 660. The groove 660 has a depth thatdecreases with increasing distance from the distal end 610. This can betermed a radial sweep defined by a depth that varies inversely as afunction of distance from a distal end of the groove 660. It can beappreciated that the groove 660 can be cut more quickly in this way thanwith in the probe electrostatic discharge machining technique.

Since the wire 620 is composed of a superelastic material, thedeflection may be relatively large without causing plastic deformation.However, this method is applicable to all elastic materials. Further,this method is applicable to all articles of manufacture and not justsurgical instruments.

In those instances where the device is intended for surgical use, theparticular material used for the elongated member (e.g., wire) should besuitable for insertion into tissue. In these cases, the wire of theinvention should be made of a noncorrosive and tough material, such as,for example, stainless steel. Further, it is preferred that the materialbe a superelastic material. The use of a superelastic material isadvantageous in that the wire can be temporarily formed into a curve ofrelatively small radius while retracted in a surgical instrument,without causing the wire to remain curved when extended from theinstrument into the tissue. An example of a noncorrosive, tough,superelastic alloy is nickel titanium per MMS-117, which is readilycommercially available from the Raychem Corporation of Menlo Park,Calif. (e.g., Ni=55.2%; Ti=44.5%; O=0.039%; Fe=0.034%; Cu=0.014%;C=0.010%; Al=0.007%; N=0.004%; Nb<0.001%; and H=0.0004%, by weight).

The particular material used for the adhesive should also be suitablefor insertion into tissue. Conveniently, the adhesive of the inventioncan be made of any biocompatible high-tack material. For themanufacturing operation, it is moreover an advantage to employ anultra-violet light curing epoxy material. The use of an ultra-violetlight curing epoxy allows the components to be repositioned while incontact with one another. Further, the use of an ultra-violet lightcuring epoxy material of low viscosity permits the adhesive to be wickedinto the groove, even after the temperature sensor leads have beenpositioned in the groove. An example of an ultraviolet light curingepoxy of low viscosity is 128-M-VLV, which is a urethane acrylate thatis readily commercially available from the DYMAX Corporation ofTorrington, Conn.

The particular material used for the temperature sensor leads shouldalso be suitable for insertion into tissue, albeit less prone to directcontact with the tissue that the wire or adhesive materials discussedabove. If, for example, the temperature sensor is a thermocouple, thesensor lead can include a first conductor of copper and a secondconductor of constantan, thereby forming a type-T thermocouple. For themanufacturing operation, it is moreover an advantage to employ annealedsensor leads so that the leads are easier to route through the grooveand undergo less work hardening. An example of such a sensor leadincludes two parallel polyester enameled circular cross-section lengthsof copper and constantan that are coated together with a layer ofpolyurethane. The outside diameter of the copper and/or constantan canbe from approximately 0.0007 inch to approximately 0.0051 inch inoutside diameter. Sensor leads in accordance with the foregoing exampleare readily commercially available from the California Fine Wire Companyof Grover Beach, Calif.

However, the particular materials selected for the wire, epoxy, andsensor leads are not essential to the invention, as long as they providethe described functions. Normally, those who make or use the inventionwill select the best commercially available materials based upon theeconomics of cost and availability, the expected applicationrequirements of the final product, and the demands of the overallmanufacturing process.

While not being limited to any particular performance indicator,preferred embodiments of the invention can be identified one at a timeby testing for the presence of low resistance to tissue insertion. Thetest for the presence of low resistance can be carried out without undueexperimentation by the use of a simple and conventional force experimentby exerting a known force against the proximal end of an embodiment ofthe invention while the distal end penetrates a simulated tissue target.The magnitude of the scalar displacement can then be measured.Alternatively, embodiments can be evaluated by determining thevariability of force needed to maintain a constant rate of travelthrough the tissue target.

EXAMPLES

Specific embodiments of the invention will now be further described bythe following, nonlimiting examples which will serve to illustrate insome detail various features of significance. The examples are intendedmerely to facilitate an understanding of ways in which the invention maybe practiced and to further enable those of skill in the art to practicethe invention. Accordingly, the examples should not be construed aslimiting the scope of the invention.

EXAMPLE 1

Referring to FIGS. 7A-7D, a wire based temperature sensing energydelivery device was formed by wire electrostatic discharge machining a0.026 inch diameter, 7.62 inch long piece of nickel titanium round crosssection wire. Referring to FIG. 7A, the resulting groove wasapproximately 0.500 inch long, approximately 0.012 inch deep andapproximately 0.010 inch wide. The round edges at the bottom of thegroove can be seen in FIG. 7A. The decreasing depth of the groove, dueto the radial sweep, can be seen in FIG. 7B. A type T thermocouple wasrouted through the groove and fixed in place with 128-M-VLV ultravioletcuring epoxy.

EXAMPLE 2

Another wire based temperature sensing energy delivery device was formedby laser welding a piece of stainless steel tube to a piece stainlesssteel round cross section wire so that a portion of the tube surroundeda portion of the wire. The tube was previously formed by fabricating asharp tip at a distal end of the tube and a temperature sensor lead slotnear a proximal end of the tube. A type T thermocouple was routedthrough the temperature sensor lead slot and through the conduit definedby the tube. The tip of the thermocouple was fixed in place at thesharpened tip of the tube with 128-M-VLV ultraviolet curing epoxy.

Practical Applications of the Invention

A practical application of the invention that has value within thetechnological arts is treating the soft palette of the mouth. Further,the invention is useful in conjunction with treating the turbinates, orin conjunction with treating the tongue, or the like. There arevirtually innumerable uses for the invention, all of which need not bedetailed here.

Advantages of the Invention

A temperature sensing electrode, representing an embodiment of theinvention, can be cost effective and advantageous for at least thefollowing reasons. The invention utilizes a solid wire instead of ahollow tube, thereby significantly reducing the cost of the resultingproduct. The invention results in a stronger, more robust electrodebecause the solid wire is more resilient and less prone to damage.

All the disclosed embodiments of the invention described herein can berealized and practiced without undue experimentation. Although the bestmode of carrying out the invention contemplated by the inventors isdisclosed above, practice of the invention is not limited thereto.Accordingly, it will be appreciated by those skilled in the art that theinvention may be practiced otherwise than as specifically describedherein.

For example, the disclosed embodiments show a circular cross-sectionwire as the structure for performing the function of penetrating tissue,but the structure for penetrating tissue can be any other structurecapable of performing the function of penetrating tissue, including, byway of example, a rod, a tube, a trocar, or even a scalpel blade, solong as the groove, or other conduit, for routing the sensor wires maybe provided therein. Similarly, the structure for penetrating tissue canhave any other cross-sectional shape, including, for instance,elliptical, rectilinear, or even parabolic.

Further, the rest of the individual components need not be formed in thedisclosed shapes, or assembled in the disclosed configuration, but couldbe provided in virtually any shape, and assembled in virtually anyconfiguration. Furthermore, the individual components need not befabricated from the disclosed materials, but could be fabricated fromvirtually any suitable materials. Furthermore, although the temperaturesensing electrode described herein is a physically separate module, itwill be manifest that the temperature sensing electrode may beintegrated into the apparatus with which it is associated. Furthermore,all the disclosed elements and features of each disclosed embodiment canbe combined with, or substituted for, the disclosed elements andfeatures of every other disclosed embodiment except where such elementsor features are mutually exclusive. For instance, a hybrid embodiment ofthe invention could combine a wire having a groove with a tube having atemperature sensor lead slot.

It will be manifest that various additions, modifications andrearrangements of the features of the invention may be made withoutdeviating from the spirit and scope of the underlying inventive concept.It is intended that the scope of the invention as defined by theappended claims and their equivalents cover all such additions,modifications, and rearrangements. The appended claims are not to beinterpreted as including means-plus-function limitations, unless such alimitation is explicitly recited in a given claim using the phrase"means-for." Expedient embodiments of the invention are differentiatedby the appended subclaims.

What is claimed is:
 1. A method of making a temperature sensing energydelivery device, the device comprising:an elongated member having agroove formed in at least portion thereof; and a first temperaturesensor mechanically connected to said elongated member, said firsttemperature sensor including a first temperature sensor lead that isrouted alone said groove; the method comprising the steps of:mounting adistal end of said elongated member so that a portion of a lengthdefined by said elongated member is held substantially rigid; bending aproximal end of said elongated member away from a principle axis definedby the distal end of said elongated member when said elongated member isnot bent; and cutting said groove with an electrostatic dischargemachining wire.